1. Technical Field of the Invention
This invention relates to cellular telephone networks, and more particularly, to a system and method of implementing multiple home location registers for a single mobile station.
2. Description of Related Art
In standard cellular radio communication networks, a subscriber's mobile telephone station is assigned a unique Mobile Subscriber Number (MSNB) and telephone number (SNB) which are associated with the Home Location Register (HLR) of the subscriber's home network. The HLR maintains mobile subscriber profile information for mobile stations having a MSNB in the MSNB series assigned to the HLR in the subscriber's home network. This profile includes, among other things, information indicative of a mobile station's location.
The SNB is the public telephone number of the mobile station and is used when operating the station in either its home or a foreign network. The SNB is a local number within the home network. If the subscriber leaves the home network, and receives a call, long distance charges are incurred by either the subscriber, the calling party, or both.
Calls to the SNB from the public switched telephone network (PSTN) are routed to a gateway mobile switching center (G-MSC) of a local cellular communications network. The G-MSC consults the subscriber's HLR via a location request (LOCREQ) invoke message for profile information regarding the location of the subscriber's mobile station and related service information. The G-MSC then forwards a routing request (ROUTREQ) invoke message from the HLR to a mobile switching center (MSC) where the subscriber's mobile station is currently located, if active. The EIA/TIA signaling standards typically followed for incoming calls to a subscriber's home network are set forth in Intersystem Signaling Standard IS-41 which is hereby incorporated by reference herein.
As currently implemented, calls to a SNB are routed through the single HLR assigned to the MSNB series of the subscriber's MSNB. If the subscriber frequently travels in a foreign network, all status inquiries are routed through the HLR of the subscriber's home network, resulting in long distance charges to both the subscriber and calling party. This is true even when both the subscriber and calling party are operating within the local calling area of the foreign network. If a subscriber desires to utilize a local number in a foreign network to avoid long distance charges, the subscriber must either significantly modify the hardware and programming of his mobile station or utilize a totally different mobile station and SNB for calls in the foreign network.
Although there are no known prior art teachings of a solution to the aforementioned deficiency and shortcoming such as that disclosed herein, a number of prior art references exist that discuss subject matter which bears some relation to the matters disclosed herein. Such prior art references are U.S. Pat. Nos. 4,677,653 and 5,437,053. Each of these references is discussed briefly below.
U.S. Pat. No. 4,677,653 to Weiner, et al (Weiner), discloses an adaptor for a cellular mobile phone unit that converts the mobile unit to operate with a plurality of telephone numbers. A plurality of read only memories (ROMs) are each programmed with a unique SNB number code that may be selectively accessed to choose a different telephone number for the mobile unit. Weiner neither teaches nor suggests, however, a means for supporting multiple SNBs without modification of the mobile telephone hardware. Weiner requires modification of the mobile unit itself, as well as connection of an adaptor to the internal microprocessor of the mobile unit.
U.S. Pat. No. 5,437,053 to Sawa, et al (Sawa), discloses a mobile telephone unit modified for storing a plurality of mobile identification numbers (MIDs). A user may select any of the stored MIDs for receiving telephone calls. When the mobile unit receives a MID transmitted from a cellular network base station, the mobile unit searches for a match between the incoming MID and one of the stored or selected MIDs. If the received MID corresponds with either a stored or selected MID, the mobile unit is enabled to communicate with the base unit. As in Weiner above, however, Sawa requires modification of the mobile telephone unit itself and neither teaches nor suggests a system or method for supporting multiple SNB without hardware modifications and programming changes to the standard mobile station.
It would be a distinct advantage to have a system and method of enabling roaming cellular subscribers to utilize unmodified mobile stations to originate or receive calls in a foreign network without incurring long distance charges. Such a system and method would enable a mobile station to receive calls on a second SNB, would be implemented entirely in the cellular network, and thus would not require hardware modification or reconfiguration of the mobile station. Review of each of the foregoing references reveals no disclosure or suggestion of a system or method such as that described and claimed herein.